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Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This 

document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the 

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1

Use of Surrogate Data at GSI

Response to SC&A Review Dated July 16, 2012

Prepared by Dave Allen, DCAS

August 2012

Background

On July 16, 2012, SC&A released a review of the use of surrogate data at GSI which evaluated the use of 

surrogate data at GSI against the Advisory Board’s Surrogate Data Criteria. This paper provides NIOSH’s

response to that review.

Overview

Unlike most Atomic Weapons Employer (AWE), the AEC contracted work at GSI did not involve active 

manipulation of uranium metal through processes such as rolling, machining, cutting, or straightening. 

The work at GSI consisted solely of taking x-rays of uranium metal that were used to evaluate the 

integrity of the casted billets manufactured at Mallinckrodt Chemical Works. Thus, the only potential 

for generation of airborne uranium at GSI would be from the movement of the metal into position for 

the examination.

Most active manipulation of uranium metal requires the metal to be heated. Typically uranium in these 

processes is heated to well over 1000 degrees Fahrenheit. At these high temperatures, the uranium 

metal oxidizes readily forming a loose oxide layer that can easily create airborne contamination. An

exception to heating uranium metal during operations is machining. When uranium metal is machined 

or cut, it is not normally preheated. Rather, the area being cut is cooled with machine oil, water or 

some other coolant. This not only reduces the release of airborne activity, but also cools the metal to 

prevent fuming.

In all cases, however, the metal is moved by various means to the furnace or equipment prior to 

working. The movement of cold uranium metal presents such a low potential for airborne uranium that 
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ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This 

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very few air samples were ever taken. Those that were, are often taken while other operations are also 

occurring causing the air in the vicinity to be contaminated by the nearby operations. Therefore, 

samples intended to be representative of the operation at GSI must consider not only the type of 

operation but the potential interferences in the vicinity.

Responses to SC&A’s Review Comments

Criterion 1: Hierarchy of Data

SC&A points out that FUSRAP contamination data from 1993 exists at GSI and could be used to estimate 

intakes, thereby eliminating the need for surrogate data. However, the hierarchy of data criterion 

adopted by the Board does not exclude the use of surrogate data when actual site data is available. The 

criterion states:

“Surrogate data should only be used to replace data if the surrogate data have some distinct 

advantage over the available data and then only after the appropriate adjustments have been 

made to reflect the uncertainty inherent in this substitution”

NIOSH agrees the use of the FUSRAP data would eliminate the need for the use of surrogate data,

however, the uncertainty associated with back extrapolating the data 40 years would likely far exceed 

the uncertainty associated with the use of more contemporaneous sources of surrogate data. Thus, 

NIOSH believes that the use of surrogate data at GSI is justified under criterion 1, given the complete 

lack of available contemporaneous monitoring data and the large degree of uncertainly inherent in 

backwards extrapolation of data collected in 1993. 

In TBD-6000, the daily average slug production airborne activity was estimated as 198 dpm/m3 by 

assuming an operator was exposed to the maximum airborne causing concentration 75% of the time. 

SC&A pointed out a mathematical error in TBD-6000 that caused the calculated geometric mean to be 

too high. SC&A also points out that while the geometric mean of the airborne contamination may be 

appropriate for lognormal distribution, Appendix BB uses it as a constant. 
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ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This 

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Appendix BB used the geometric mean as a constant instead of a lognormal distribution because the 

airborne concentration TBD-6000 is associated with slug production rather than simply moving cold 

uranium metal. The use of the geometric mean is an attempt to prevent the value from being 

unrealistically high (i.e., it represents a plausible upper bound) as SC&A appears to indicate in their 

review of criterion 5. 

Criterion 2: Exclusivity Constraints

This criterion requires the use of surrogate data to be stringently justified. SC&A points out that the 

basis for selecting the surrogate data used by NIOSH was that uranium handling alone results in less 

disturbance of the metal than the other scenarios listed in Battelle-TBD-6000. That is, the data used are 

higher than the exposure conditions that existed at GSI. SC&A does not believe this qualifies as 

stringently justified.

NIOSH agrees the use of surrogate data at GSI has not been stringently justified in Appendix BB. 

However, Appendix BB was written approximately three years prior to the Board formally adopting its 

surrogate data criteria. In response to SC&A’s comment, NIOSH has reviewed the airborne exposure 

data available from a number of sites to determine if a more comprehensive dataset are available to 

satisfy the intent of this criterion. At the end of this paper NIOSH provides a more robust analysis of 

the use of surrogate data at GSI (see section titled Evaluation of Other Sources of Surrogate Data) with

the intent to incorporate relevant parts in the next revision to Appendix BB.

Criterion 3: Site or Process Similarities

SC&A points out that slug production by powder metallurgy is not similar to x-raying uranium metal. As 

discussed previously, each task in TBD-6000 inherently includes the movement of cold uranium metal at 

some step in the particular process. In the slug production process described in Harris and Kingsley1

, the 

process starts with a uranium metal ingot loaded into a hydriding furnace. In the process, a uranium 

 1 Harris, W.B., and I. Kingsley, 1959. “The Industrial Hygiene of Uranium Fabrication,” A.M.A.

Archives of Industrial Health, 19, 540–565.
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Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This 

document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

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hydride is formed and later dehydrided to form a metal powder that is shaped into slugs. As with each 

process described in TBD-6000, the airborne contamination from this movement of cold uranium metal 

is not quantified so Appendix BB used one of the lowest airborne creating tasks as a bounding estimate 

of the movement of cold uranium metal. While the task as a whole is not representative of the 

movement of cold uranium metal, the movement of cold uranium metal is included in the task. 

Criterion 4: Temporal Considerations 

SC&A notes that the data used was likely collected prior to 1958 which is therefore not 

contemporaneous with the end of the operational in 1966. However, the Board’s criterion indicates the 

data should be from the same general period unless it can be demonstrated that the “working 

conditions, procedures, monitoring methods, and (perhaps) legal requirements were comparable to the 

period in question”. 

In addressing this, we note that there has never been any indication of any intentional controls over 

airborne contamination at GSI. The source of airborne uranium was simply movement of cold uranium 

metal in order to position it for x-ray examination. The source of airborne is then a physical 

characteristic of uranium metal which doesn’t change over time.

Criterion 5: Plausibility

SC&A appears to be indicating the airborne contamination calculation in Appendix BB is not plausible 

because uranium work at GSI was intermittent and thus “large flakes” of uranium oxides would not be 

quickly ground into dust under foot or forklift traffic. This results in the equilibrium value in Harris and 

Kingsley for a continuous operation being higher than that expected at GSI.

NIOSH agrees that work with uranium at GSI was intermittent and thus it is less likely that an equilibrium 

concentration would be reached. This implies the value in Appendix BB is too high. However, the 

argument used by SC&A appears to be based on the idea that the resuspension of surface 

contamination is the major source of airborne contamination during operational periods. 
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Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This 

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In reality, airborne contamination while working with uranium metal would initially be caused entirely 

by disturbing uranium oxides on the surface of the uranium metal. This contamination would be 

relatively consistent from one piece of uranium to the next. As additional pieces of uranium metal are 

brought in, a fresh source of contamination is available. Since this source of airborne does not depend 

on the slow buildup of contamination, it occurs immediately and builds up quickly to a maximum. 

The other source of airborne, resuspension from surface contamination, will build up to a maximum 

more slowly as the surface contamination builds up from continued operations. This source of airborne 

is much lower than the operational source. This effect can be seen in Figure 1 which depicts the relative 

levels of airborne contamination during operational and post-operational period at Simonds Saw and 

Steel. The time scale in this figure is days. Once the rolling operations end, the airborne contamination 

decreases quickly to a steady level caused by resuspension. It should be noted that, at Simonds Saw and 

Steel, the uranium metal was heated and rolled resulting in a much larger fraction of the metal being

oxidized. This would result in higher levels of airborne and surface contamination than would be seen 

with the movement of cold uranium.
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Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This 

document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

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Figure 1 – Airborne Uranium at Simonds Saw and Steel During and After Rolling Operations
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Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This 

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7

Evaluation of Other Sources of Surrogate Data

As described earlier, monitoring data associated with the movement of cold uranium metal is limited. A 

review of the data from AWE facilities indicate that most data are associated with actual airborne 

causing activities, rather than simply moving the metal. Also, some sample results that are associated 

with moving the metal are positively biased by nearby work with uranium metal. In searching the 

available data from a number of AWEs, however, a few examples were found.

Heald Machine Company (SRDB 40986 page 10, Figure 2 in this paper) 

At the Heald Machine Company, air samples were taken while machining uranium metal slugs. Values 

ranged from 1 to 11 dpm/m3

. It is likely coolant was used to cool and lubricate the uranium while it was 

being machined so air samples while machining were not necessarily representative of uranium metal 

handling. However, coolant is normally supplied by a fixed nozzle on the machine. Thus, dry uranium 

metal would be moved to the machine prior to machining. If significant airborne contamination was 

caused by this movement, it would still be present while machining the slugs. Although this activity may 

not be directly applicable to the movement of cold uranium metal, they do provide an indication that

actual values are relatively low.

Chambersburg Engineering Co (SRDB 10048 page 39, Figure 3 in this paper)

At Chambersburg Engineering approximately 150 hot uranium slugs were forged into washers during a 

two day test. The slugs were dry heated and no ventilation was provided for the work. A summary of 

the air samples are provided in Figure 3. The average air concentration while loading cold uranium slugs 

into a furnace was 69 dpm/m3 while loading one slug every 15 minutes and increased to 77 while 

loading one slug every two minutes. The maximum air concentration while loading cold uranium into 

the furnace was 174 dpm/m3

. Air concentrations after heating and while forging were higher and it is 

possible some of that airborne contamination caused by this work interfered with samples taken while 

loading the furnace.

R. W. Leblond Machine Tool Co. (SRDB 10634 page 11, Figure 4 in this paper)
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A test was conducted at Leblond to evaluate a hole boring machine. Air samples were taken while 

boring a hole into a uranium billet with a rapid bore machine. Coolant was used while boring the hole 

but air samples were taken while loading the dry billet onto the machine. The first thee samples on the 

data sheet (Figure 4) were taken as breathing zone air samples while “hooking hoist to billet and placing 

billet into position on machine”. The remarks section of the data sheet indicates there was no 

ventilation on the machine and very little air movement. Coolant used during the boring reduced any 

possible interference from nearby operations. Together, these issues make the Lablond samples the 

most directly relevant samples to the work at GSI. One of the samples measured 9 dpm/m3 while the 

other two samples had results that were labeled as “nd” which stands for none detected. 

Conclusions

While it is difficult to find air sample data representative of moving cold uranium metal, it must be 

realized that this movement is inherent with every operation involving uranium metal. If the movement 

were to cause high levels of airborne uranium, it would in most cases continue to be present during the 

tasks for which samples were taken. The most relevant samples to GSI discussed in this paper are those 

taken at Leblond, which involved moving an ingot to a boring machine. Because this data set contains 

only three samples collected over a one day period, it is not a very robust sample set. Samples taken at 

Chambersburg Engineering while loading cold uranium slugs into a furnace were as high as 174 dpm/m3

. 

While it is very possible some of this airborne activity was caused by nearby operations, it is not 

definitely known. Therefore, it is possible that handling cold uranium metal could cause airborne 

activity this high. This is relatively close to the 198 dpm/m3 used in Appendix BB. 

The value used in Appendix BB, therefore, appears to be bounding without increasing it by a factor of 

2.9 as suggested by SC&A in criterion 1. It also appears to be a plausible upper bound when the degree 

of uncertainty is taken into consideration, rather than implausibly high as implied in SC&A criterion 5. 

The process of moving cold uranium metal without special controls or ventilation is a function of the 

physical characteristics of uranium metal and not a function of the time frame in which the samples 

were taken (criterion 4). While the processes described in TBD-6000 are based on sources of airborne 

contamination with greater potential to generate airborne activity than merely the movement of 
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Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This 

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9

uranium metal, they do include the movement of metal and therefore represent work at GSI in part 

(criteria 3). Lastly, it is NIOHS’s position that, while it is difficult to find air samples that perfectly match 

the exposure condition at GSI, the value used in Appendix BB is both plausible and bounding. It is 

believed that this paper provides justification for its use and applicable portions of this justification will 

be incorporated in the next revision to Appendix BB (criterion 2). 
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Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This 

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Figure 2 – Airborne Uranium Data Sheet from Heald Machine Company
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Figure 3 – Airborne Uranium Summary from Chambersburg Engineering
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Figure 4 – Airborne Uranium Data Sheet from Leblond